Dura-Ace 7800 Compatibility
04-12-19, 11:46 PM
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Dura-Ace 7800 Compatibility
Hi there! Just bought a vintage tri bike with Dura-Ace 7800. Need to replace the crank arms. They currently have 170 and the bike is a very small bike and I am also very small so want max 165. I live in a country where there is a poor selection of used parts as well as a poor selection of "small people parts" so a used 165 crank arm that is 7800 is probably never going to be an option.
I assume ultegra 6600 and 6700 would work? What else might work? Bike is 10sp obviously and I don't know if 11sp would fit on the wheel set and am not really wanting to upgrade the whole thing due to costs. Wondering what my other compatible options are here. Have considered a new crank but again, a new 10sp crank that is compatible with 7800....? Looking for options I guess. Hate to ruin that it's all dura ace gruppo but in this case, it is what it is. Thanks.
I assume ultegra 6600 and 6700 would work? What else might work? Bike is 10sp obviously and I don't know if 11sp would fit on the wheel set and am not really wanting to upgrade the whole thing due to costs. Wondering what my other compatible options are here. Have considered a new crank but again, a new 10sp crank that is compatible with 7800....? Looking for options I guess. Hate to ruin that it's all dura ace gruppo but in this case, it is what it is. Thanks.
04-13-19, 02:34 AM
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Cranks and chainrings, don't really care about what speed the cassette is between 9-11.
For a replacement, you already have a very limited choice if you're looking for a 165mm, so you will probably have to have whatever you can get. For your 6600 and 6700 options, both are long OOP, would steer away from 6700, it looks nicer than 6600, but the outer chainring is a unique design, specific to the 6700, and once the outer goes, it's cheaper to just buy a replacement crank, than replace the outer (been there, scrapped the crank)
For availability, your on the internet, can you not order from another country if you need the item and can not source it locally?
For 7800, it's old now, the shifters were nice, the FD's looked nice, till they corroded and broke (had a few of these fail, and only Shimano FD's I have ever had with significant corrosion). Keeping a complete groupset on a bike is a nice idea, but 7800 is 4 generations/12 years OOP now, so getting replacement parts may be hard now.
For a replacement, you already have a very limited choice if you're looking for a 165mm, so you will probably have to have whatever you can get. For your 6600 and 6700 options, both are long OOP, would steer away from 6700, it looks nicer than 6600, but the outer chainring is a unique design, specific to the 6700, and once the outer goes, it's cheaper to just buy a replacement crank, than replace the outer (been there, scrapped the crank)
For availability, your on the internet, can you not order from another country if you need the item and can not source it locally?
For 7800, it's old now, the shifters were nice, the FD's looked nice, till they corroded and broke (had a few of these fail, and only Shimano FD's I have ever had with significant corrosion). Keeping a complete groupset on a bike is a nice idea, but 7800 is 4 generations/12 years OOP now, so getting replacement parts may be hard now.
04-14-19, 04:59 AM
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Hi. Thank you for your reply but what is OOP? Like I said, I don't really care about keeping the whole group set the same or not but only the arms are the issue so prefer not to change everything just because the arms do not work.
I am looking for info regarding which arms I can just switch out or which other cranksets will work. For example, can Shimano 105 5750 work? Perhaps I was hoping for too much here as I thought maybe somebody would do me a favor and list 3-4 crank brands/ models that would be possible so I could just order them. I would actually prefer to go even shorter than 165 but know I'd have to invest in specialty brands for that and am not yet ready to pay for that... unless someone knows of a company that makes compatible arms for a reasonable price.
Perhaps I should add... I own ultegra 6600/6603 arms in 165. I should have maybe asked if anyone knows if they should work on the dura ace 7800, which is a double...or if there is some sort of Q factor change that would not be quite as nice...
I am looking for info regarding which arms I can just switch out or which other cranksets will work. For example, can Shimano 105 5750 work? Perhaps I was hoping for too much here as I thought maybe somebody would do me a favor and list 3-4 crank brands/ models that would be possible so I could just order them. I would actually prefer to go even shorter than 165 but know I'd have to invest in specialty brands for that and am not yet ready to pay for that... unless someone knows of a company that makes compatible arms for a reasonable price.
Perhaps I should add... I own ultegra 6600/6603 arms in 165. I should have maybe asked if anyone knows if they should work on the dura ace 7800, which is a double...or if there is some sort of Q factor change that would not be quite as nice...
Last edited by Lasue; 04-14-19 at 05:24 AM.
04-14-19, 07:11 AM
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OOP= Out Of Production i.e. discontinued. As jimc101 noted these cranks have been discontinued for several years and you will have to find one NOS (new old stock) or used.
04-14-19, 07:59 AM
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6603 uses spacers (10 & 16) to hit the 45mm chainline. https://si.shimano.com/pdfs/ev/EV-FC-6603-2366E.pdf
https://si.shimano.com/#/en/search/C...heel&type=ROAD
Celebrazio: Bicycling - Shimano Road Bike Parts Compatibility - 2006
https://si.shimano.com/#/en/search/C...heel&type=ROAD
Celebrazio: Bicycling - Shimano Road Bike Parts Compatibility - 2006
04-14-19, 11:09 PM
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dedhed- THANKS!!! You really gave me some great links!
Your first link makes it look like the spacers are removable and as you mention, these make the 45mm chainline so probably if I just remove the spacers, I can get to the 43.5mm for the double, so I guess the actual arms and axle are the same on the 6600 and 6603?
Forgive me but I have one further question, in the Shimano specifications documents it says, e.g. "bolt circle diameter" and for the 6603 "130mm/74mm". The second number is for the inner chain ring right? So technically is not as problematic since I will not have an inner, since moving the 6603 arms to a 7800? It looks like the 7803 and 6603 inner bolt circle diameters were different.
If this works, I'm super excited because stealing the arms from my road bike to put on the tri bike means I have an excuse to upgrade my old Litespeed road bike to a newer double compact. Maybe I can just minimize the tolerance of the 6603 STI levers and FD and only have to change the crank.... That'd be amazing.
On a side note...Does anyone know a company still producing 650c carbon wheels? Seems the usual guys, HED, Zipp, DT Swiss aren't making 650c anymore...
Your first link makes it look like the spacers are removable and as you mention, these make the 45mm chainline so probably if I just remove the spacers, I can get to the 43.5mm for the double, so I guess the actual arms and axle are the same on the 6600 and 6603?
Forgive me but I have one further question, in the Shimano specifications documents it says, e.g. "bolt circle diameter" and for the 6603 "130mm/74mm". The second number is for the inner chain ring right? So technically is not as problematic since I will not have an inner, since moving the 6603 arms to a 7800? It looks like the 7803 and 6603 inner bolt circle diameters were different.
If this works, I'm super excited because stealing the arms from my road bike to put on the tri bike means I have an excuse to upgrade my old Litespeed road bike to a newer double compact. Maybe I can just minimize the tolerance of the 6603 STI levers and FD and only have to change the crank.... That'd be amazing.
On a side note...Does anyone know a company still producing 650c carbon wheels? Seems the usual guys, HED, Zipp, DT Swiss aren't making 650c anymore...
04-16-19, 05:03 PM
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dedhed- THANKS!!! You really gave me some great links!
Your first link makes it look like the spacers are removable and as you mention, these make the 45mm chainline so probably if I just remove the spacers, I can get to the 43.5mm for the double, so I guess the actual arms and axle are the same on the 6600 and 6603? I don't know that to be a fact. They use the same BB, so If they were the same, the arm would be too long with the spacers removed as the NDS (LH) arm only goes on to a certain point for the #7 safety plate to engage the groove. Or you can move both spacers to one side and be offset a bit. #16 actually sets the chainline as it sits on the DS but it is 6.5mm
Forgive me but I have one further question, in the Shimano specifications documents it says, e.g. "bolt circle diameter" and for the 6603 "130mm/74mm". The second number is for the inner chain ring right? Yes So technically is not as problematic since I will not have an inner, since moving the 6603 arms to a 7800? It looks like the 7803 and 6603 inner bolt circle diameters were different. The 6603 "inner" 30t would go on the 74mm bcd and the 39 middle mounts on the same 130 bcd as the outer. I believe the 7803 inner is 92mm bcd
If this works, I'm super excited because stealing the arms from my road bike to put on the tri bike means I have an excuse to upgrade my old Litespeed road bike to a newer double compact. Maybe I can just minimize the tolerance of the 6603 STI levers and FD and only have to change the crank.... That'd be amazing.
On a side note...Does anyone know a company still producing 650c carbon wheels? Seems the usual guys, HED, Zipp, DT Swiss aren't making 650c anymore...
Your first link makes it look like the spacers are removable and as you mention, these make the 45mm chainline so probably if I just remove the spacers, I can get to the 43.5mm for the double, so I guess the actual arms and axle are the same on the 6600 and 6603? I don't know that to be a fact. They use the same BB, so If they were the same, the arm would be too long with the spacers removed as the NDS (LH) arm only goes on to a certain point for the #7 safety plate to engage the groove. Or you can move both spacers to one side and be offset a bit. #16 actually sets the chainline as it sits on the DS but it is 6.5mm
Forgive me but I have one further question, in the Shimano specifications documents it says, e.g. "bolt circle diameter" and for the 6603 "130mm/74mm". The second number is for the inner chain ring right? Yes So technically is not as problematic since I will not have an inner, since moving the 6603 arms to a 7800? It looks like the 7803 and 6603 inner bolt circle diameters were different. The 6603 "inner" 30t would go on the 74mm bcd and the 39 middle mounts on the same 130 bcd as the outer. I believe the 7803 inner is 92mm bcd
If this works, I'm super excited because stealing the arms from my road bike to put on the tri bike means I have an excuse to upgrade my old Litespeed road bike to a newer double compact. Maybe I can just minimize the tolerance of the 6603 STI levers and FD and only have to change the crank.... That'd be amazing.
On a side note...Does anyone know a company still producing 650c carbon wheels? Seems the usual guys, HED, Zipp, DT Swiss aren't making 650c anymore...
